attaching ground wire in this box

update.

I got the bath exhaust fan wired to this light box with 12-2 romex, and of course there is the extra ground wire hanging there.

I don't think this box is grounded. Back in the 60's, maybe the vanity lights were never grounded. The light switch controlling the light certainly has no ground wire. On the other hand, the sink outlet is armored cable, so I have no idea if the whole house was wired with armored cable.

Anyhow, I just shoved the new ground wire back in the box. Didn't screw it to anything.